(628f) Ionic Liquids Based Composite Membranes for CO2 Separation

Authors: 
Bai, L. - Presenter, Institute of Process Engineering, Chinese Academy of Sciences
Zhang, C., Institute of Process Engineering, Chinese Academy of Sciences
Yang, B., Institute of Process Engineering, Chinese Academy of Sciences
Han, J., Institute of Process Engineering, Chinese Academy of Sciences
Zhang, X., Beijing Key Laboratory of Ionic Liquids Clean Process,CAS Key Labroratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences
A large number of CO2 emissions have caused global warming, bringing some serious disasters like ice melting, sea level rising, floods, et al. It is a worldwide concern and urgent to reduce CO2 emissions. Among available measures, CO2 capture and storage (CCS) is recognized as one of feasible methods, in which efficient CO2 capture and separation is critical. Additionally, the removal of CO2 is an important part in the gas purification of syngas, natural gas and biogas. Therefore, the efficient capture and separation of CO2 is greatly significant for sustainable development of ecosystem, economy and society. Ionic liquids (ILs) as a novel solvent possess negligible vapor pressure, good stability and structural design, making them widely applied in gas separation (CO2, SO2, NH3 etc.), especially CO2 separation1. Due to these unique properties, ILs have been used in membrane systems including supporting liquid membranes, membrane contactors and composite membranes to improve the stability and gas performance2. Three-component composite membranes containing ILs, nano-materials and polymers, will be a promising approach to simultaneously obtain optimal gas separation performance and excellent stability of membranes.

In this work, a series of phosphonium based ILs ([P66614][NTf2], [P66614][DCA], [P66614][Triz] were synthesized and blended with polyether copolyamide (Pebax) to prepare IL/Pebax composite membranes for CO2 separation. The results showed that the [P66614][NTf2]/Pebax composite membrane has the best performance, with the CO2 permeability up to 244.3 Barrer, when the IL content reached 40 wt%. With the increase of IL content, the CO2 permeability of [P66614][NTf2]/Pebax composite membrane increased. In order to further improve the separation performance and strengthen the mechanical property of the membranes, ZIF-8 porous particles were added to form three-component composite membranes and the single gas permeability and CO2 selectivity was systematically investigated. The results showed that the gas permeability of the membrane increases as the content of [P66614][NTf2] increases. When the content of [P66614][NTf2] reaches 30 wt% and the content of ZIF-8 is 10 wt%, the CO2 permeability of the membrane is up to 386.8 Barrer while the CO2 selectivity keeping constant. The various characterization including FTIR, DSC and SEM revealed that the addition of IL increases the free volume of the membrane and reduces the agglomeration of ZIF-8 particles, which promotes gas diffusion and hence improves the CO2 permeability of the membranes.

References:

1. Zeng, S. J.; Zhang, X. P.; Bai, L.; Zhang, X. C.; Wang, H.; Wang, J. J.; Bao, D.; Li, M. D.; Liu, X. Y.; Zhang, S. J., Ionic-Liquid-Based CO2 Capture Systems: Structure, Interaction and Process. Chemical Reviews, 2017, 117: 9625-9673.

2. Dai, Z.; Noble, R. D.; Gin, D. L.; Zhang, X.; Deng, L., Combination of ionic liquids with membrane technology: A new approach for CO2 separation. Journal of Membrane Science, 2016, 497: 1-20.

Corresponding author’s e-mail address: xpzhang@ipe.ac.cn